Enable overriding the service setup host python interpreter

In order to enable the service setup host python interpreter to
be changed easily, we make it a variable. This will be useful
when someone sets the service setup host to be the utility
container, because we'll be able to set this var by default.

Change-Id: I3ad7e3006180b0790232b0a6ccd4b57e5be7a30d

defaults/main.yml

@@ -20,6 +20,7 @@ debug: False
 # for the service setup. The host must already have
 # clouds.yaml properly configured.
 octavia_service_setup_host: "{{ openstack_service_setup_host | default('localhost') }}"
+octavia_service_setup_host_python_interpreter: "{{ openstack_service_setup_host_python_interpreter | default((octavia_service_setup_host == 'localhost') | ternary(ansible_playbook_python, ansible_python['executable'])) }}"
 
 ## Octavia standalone (v2) experimental
 octavia_v2: True

tasks/octavia_service_add.yml

@@ -21,8 +21,7 @@
 - name: Setup the service
   delegate_to: "{{ octavia_service_setup_host }}"
   vars:
-    ansible_python_interpreter: >-
-      {{ (octavia_service_setup_host == 'localhost') | ternary(ansible_playbook_python, ansible_python['executable']) }}
+    ansible_python_interpreter: "{{ octavia_service_setup_host_python_interpreter }}"
   block:
     - name: Add service to the keystone service catalog
       os_keystone_service: